Thematic maps show both location and value. This requires that you have boundaries on a map, data associated with the boundaries, and matching primary IDs between the boundaries (areas, curves, and points) and the data file. See Linking Data to Boundaries for more information on primary IDs and linking data.
In general terms, to make a thematic map in MapViewer, you must:
1. Import a boundary map.
2. Specify the data file to use with the map.
3. Indicate the location of the primary ID in the data file.
4. Indicate the variable column that contains the data you want to portray on the map.
Creating a Thematic Map
The procedure for creating thematic maps is essentially the same for all thematic map types. So, the procedure for creating a hatch map is the same as the procedure for creating a prism map, etc. As an example, let's make a hatch map of Ohio population.
1. In a new map window, choose the Map | Create Map | Hatch command . The Import Boundary File dialog is displayed prompting you to select the boundary file to use for the map. Browse to the SAMPLES folder and double-click the OH2000.GSB file. If the GS Boundary Import Options dialog appears, do not check the Areas to Curves box, and then click the OK button.
2. The Import Options dialog appears so you can select IDs for the boundary file. The Create PID box should be checked and the ID should be Primary. Uncheck the Create Hyperlink box since there are no hyperlinks associated with the boundary file. Checking the rest of the boxes is optional. Click the OK button.
3. Next, the Open Data File dialog is displayed. Double-click the OH2000.DAT file.
4. The Hatch Map dialog is displayed. Verify that the PID (primary ID) column is set to the correct column in the data file, in this case, Column A: FIPS CODE. This column in the data file matches the primary ID selected for the boundaries in the Import Options dialog.
5. Select Column C: POP 2000 from the Variable list.
6. Click the OK button and a hatch map of Ohio population is created.
Switching to Another Map Type
Switching to another map type is quite simple. Since the boundary and data files are already loaded, you can select a new map type and the available information is reused. Choose the new map type (such as the Density Map command) to display the dialog for the map type. Click the OK button in the map properties dialog and the new map showing population in the new map style is displayed.
Changing the Map Properties
To make changes to the map after it is created, you can open the map properties by:
Edit map properties in the Property Manager
The Property Manager pages for that map type is displayed after using one of the methods listed above. For example, you can change the Variable column to display different data on your map or you can change the data file used to create the map.
Adding More Boundaries to Your Map
After you have created a thematic map, you can add boundaries to the existing map. The boundaries are included as part of the thematic map if they have the appropriate link to data. When you import new boundaries to the map, you should use the Append image option in the Import Boundary Files dialog. This assures that the incoming boundaries and the existing boundaries are drawn in the correct relative positions. If you do not want the boundaries to be appended, you can switch off the Append image option and the incoming boundaries are drawn as if the window is empty and are scaled to fit the page without regard for the existing boundaries.
You can also draw additional boundaries and add primary IDs to the boundaries you draw. After a boundary is drawn, you can add a primary ID by typing it into the Object Manager or Property Manager.
Creating Custom Boundaries
Linking Data to Boundaries - The Primary ID
What is a Thematic Map?